Erroneous Readings
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Posts: 46,084
Good folks,
I am working on a project where I have an A/D convertor hooked to a
BS2 that outputs the results to a 3 digit LED display.
It reads accurate everytime while the Laptop computer is hooked to
the stamp but gives intermittent false reading when disconnected.
Does the programming port need terminated?
Any help would be appreciated.
Kirk
I am working on a project where I have an A/D convertor hooked to a
BS2 that outputs the results to a 3 digit LED display.
It reads accurate everytime while the Laptop computer is hooked to
the stamp but gives intermittent false reading when disconnected.
Does the programming port need terminated?
Any help would be appreciated.
Kirk
Comments
No, the programming port does not need termination.
However it is a good idea to "terminate" the stamp's ATN line.
100n
DTR ----||---+---+--- ATN
| |
_|_ /
100n --- \3k3 the resistor is optional
| / but recommended
_|_ _|_
hope the artwork arrives intact
Is the erroneous reading just in the moment when you disconnect the
laptop, or always as soon as it is disconnected?
Could it probably be that your stamp resets occasionally when
disconnected from the laptop?
I would check groundings an power supply tracks.
Regards
Adrian
3.3.k parallel to the cap that is already on most Stamp (Parallax produced)
commercial boards.
Original Message
From: Adrian Schneider [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=XEsJD-r7a9wCG3DsVUFX3C98DT55crnoklE9oZAbkAgAewBLSwQqO3-wySbN_2HGTAtfby6llnWCuWdle92AZRFVBQaaXtq02A]adrian.schneider@t...[/url
Sent: Tuesday, June 17, 2003 10:28 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: Erroneous Readings
Hi Kirk
No, the programming port does not need termination.
However it is a good idea to "terminate" the stamp's ATN line.
100n
DTR ----||---+---+--- ATN
| |
_|_ /
100n --- \3k3 the resistor is optional
| / but recommended
_|_ _|_
hope the artwork arrives intact
Is the erroneous reading just in the moment when you disconnect the
laptop, or always as soon as it is disconnected?
Could it probably be that your stamp resets occasionally when
disconnected from the laptop?
I would check groundings an power supply tracks.
Regards
Adrian
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[noparse][[/noparse]Non-text portions of this message have been removed]
I do not have a 3K resistor on the ATN line to ground but will try
that and let you know.
This is a scales. It turns on power to Stamp/ADC/Display when weight
is applied. There is a delay for voltages to stabalize then it
samples the weight (Load Cell) 8 times over 2 seconds then averages
them and displays it on the LED display for 5 seconds then shuts
down.
It has never failed to read correctly with the computer hooked up.
The only other thing I notices was a negative voltage on the TX/RX
line out of the laptop to ground.
Thanks again for the help.
Kirk
--- In basicstamps@yahoogroups.com, Sadler Porter
<porter.sadler@s...> wrote:
> The drawing is not quite intact but I assume that are suggesting to
add a
> 3.3.k parallel to the cap that is already on most Stamp (Parallax
produced)
> commercial boards.
>
>
>
>
Original Message
> From: Adrian Schneider [noparse][[/noparse]mailto:adrian.schneider@t...]
> Sent: Tuesday, June 17, 2003 10:28 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Re: Erroneous Readings
>
> Hi Kirk
>
> No, the programming port does not need termination.
> However it is a good idea to "terminate" the stamp's ATN line.
>
> 100n
> DTR ----||---+---+--- ATN
> | |
> _|_ /
> 100n --- \3k3 the resistor is optional
> | / but recommended
> _|_ _|_
>
> hope the artwork arrives intact
>
> Is the erroneous reading just in the moment when you disconnect the
> laptop, or always as soon as it is disconnected?
> Could it probably be that your stamp resets occasionally when
> disconnected from the laptop?
> I would check groundings an power supply tracks.
>
> Regards
> Adrian
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
>
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
The negative voltage you mentionned, is formed by that transistor
network at frontend of the stamp's Rx/Tx lines. Its supply comes
from the connected computer (your laptop in this case).
It is only neccessary to make the Rx/Tx lines - which are TTL
otherwise - compliant with the requirements of the RS232 standard.
If you already have the caps between ATN/DTR the resistor probably
will not change a lot.
BTW: when you disconnect the laptop, did you remove the cable
from your circuit? If you leave it dangling it could pick up
noise and cause the erroneous behaveiour of your circuit.
could you probably provide a circuit diagram?
Regards
Adrian
My programming cable off the Stamp is only 6" long.
I have a 6'cable from there to the Laptop.
It is just when I unplug both from the laptop that the problem starts.
Then I can not to a "debug" to see where the error occurs.
I will post a schematic and program later.
I may have a shielding problem since I have all the components in a small area.
I am going to run some monitoring leads out to see if the problem is the if I
can isolate the problem.
Thanks for the help. Must work for a living now.
Kirk
Original Message
From: Adrian Schneider [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=B_et4-xH150shDOK9Xa6kn97j5BDkYFGoQ7x1ER6pyZeiFB92l8fnL0Pc2pH4_LNyiJxRU3ZAUO_J4XNmo3hrLcGxu_A]adrian.schneider@t...[/url
Sent: Wednesday, June 18, 2003 1:35 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: Erroneous Readings
Hi Kirk
The negative voltage you mentionned, is formed by that transistor
network at frontend of the stamp's Rx/Tx lines. Its supply comes
from the connected computer (your laptop in this case).
It is only neccessary to make the Rx/Tx lines - which are TTL
otherwise - compliant with the requirements of the RS232 standard.
If you already have the caps between ATN/DTR the resistor probably
will not change a lot.
BTW: when you disconnect the laptop, did you remove the cable
from your circuit? If you leave it dangling it could pick up
noise and cause the erroneous behaveiour of your circuit.
could you probably provide a circuit diagram?
Regards
Adrian
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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disconnected from the laptop? If so, try it with the cables
disconnected. Also, put a 0.1uf capacitor in parallel with the 3kohm
resistor on the ATN pin.
Since you can't use the debug window, instead, put an LED or a piezo
speaker on a free output pin, and make it do something at the very
top of your program to check for resetting.
I ran into a weird problem the other daym where a stamp was seemingly
locked up on a SERIN command on p16. This was a SERIN with timeout,
but it would never time out. The Stamp was not resetting. A 6 foot
RS232 cable was still attached to the programming port, and the
problem disappeared when the cable was disconnected. When I looked
at the Rx and Tx lines, at first I didn't see anything, but the scope
was triggering on something. It turned out there was a pulse just a
couple of microseconds wide, recurring with a period of several
milliseconds, on both the Rx and Tx lines. It was some kind of
internal oscillation in the Rx/Tx circuit, coupled by the cable
capacitance. I need to look at it more closely. But it is just one
more reason for not leaving an unterminated cable attached to the
Stamp programming port.
-- Tracy
>The resistor did not help but good try.
>My programming cable off the Stamp is only 6" long.
>I have a 6'cable from there to the Laptop.
>It is just when I unplug both from the laptop that the problem starts.
>Then I can not to a "debug" to see where the error occurs.
>I will post a schematic and program later.
>
>I may have a shielding problem since I have all the components in a
>small area.
>
>I am going to run some monitoring leads out to see if the problem is
>the if I can isolate the problem.
>Thanks for the help. Must work for a living now.
>Kirk
>
>
>
Original Message
>From: Adrian Schneider [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=NAnEhlcKhQ0QF-1Ld-759UEojI8EvkiMnvXb8E0U2ZAQ7Wh-wYJWVDLGylKq3hiiI-lPM8IOsVQpV5G3ZEiblDFCFi2zAYksKg]adrian.schneider@t...[/url
>Sent: Wednesday, June 18, 2003 1:35 AM
>To: basicstamps@yahoogroups.com
>Subject: [noparse][[/noparse]basicstamps] Re: Erroneous Readings
>
>
>Hi Kirk
>
>The negative voltage you mentionned, is formed by that transistor
>network at frontend of the stamp's Rx/Tx lines. Its supply comes
>from the connected computer (your laptop in this case).
>It is only neccessary to make the Rx/Tx lines - which are TTL
>otherwise - compliant with the requirements of the RS232 standard.
>
>If you already have the caps between ATN/DTR the resistor probably
>will not change a lot.
>
>BTW: when you disconnect the laptop, did you remove the cable
>from your circuit? If you leave it dangling it could pick up
>noise and cause the erroneous behaveiour of your circuit.
>
>could you probably provide a circuit diagram?
>
>Regards
>Adrian
>
>
>To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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>Subject and Body of the message will be ignored.
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>
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>
>
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>from the same email address that you subscribed. Text in the
>Subject and Body of the message will be ignored.
>
>
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